1. Field of the Invention
The present invention relates to a data flow control apparatus for outputting data through a switchover and a memory apparatus in which such a data flow control apparatus is incorporated, and more particularly to a data flow control apparatus used as means for preventing an illegal copy of softwares in a control system or a game system such as a computer game, and the like, which are controlled by a CPU (Central Processing U nit) and a software, and a memory apparatus in which such a control apparatus is built.
2. Description of the Related Art
For example, as shown in FIG. 33, the conventional control system comprises a CRT 2, a CPU 3, a ROM 4, a terminal 5 and an SRAM 6 which all are coupled to a data bus 1.
According to such a control system, in general, a software is stored in the ROM 4, and is selectively processed in accordance with an instruction for starting the software from the terminal 5. A processing result is displayed on the CRT 2. When it is required during the processing to temporarily store the data, the SRAM 6 is utilized. Alternately, it also happens that a part of the software is down loaded from the ROM 4 on the SRAM 6 and be subjected to the processing by the CPU 3.
The software stored in the ROM 4 is arranged, as shown in FIG. 34, in such a manner that various data "D" are each stored in the associated address "A" indicating the storage address of the data. Thus, the software is executed in the CPU 3 by the use of data D outputted in compliance with the address A issued from the CPU 3.
In the above described control system or a game system adopting such a control system, a portion of the ROM 4 shown in FIG. 33 is detachably arranged on a cassette basis. Thus, when a cassette 9 is interchanged, there is performed a control according to a storage content of the ROM 4 which the cassette 9 is equipped with, or a person may enjoy the game according to the storage content.
A cassette type arrangement of the portion of the ROM 4 for accommodating the software permits the content of the ROM 4 or data D to be outputted to a data line 8 by means of simply applying the address A via an address line 7.
Thus, such a simple structure allows an illegal copy of the software through reading all data D by means of sequentially applying all addresses A. This causes such a serious problem that a profit of a proper rightful person concerning with the software, which would be developed through investing a lot of money and labor and taking up a lot of time, is damaged.